The Killer Storm
by Lynyrd Lionheart
Summary: When a tragedy leaves Klaus with skin like ice desperate for warmth, and without a fiancee, he believes he has no hope left. Until he meets Firestorm, who he is positive is the love of his life, Caroline Forbes. If only she could remember... and if only he could touch her without wanting to suck all the warmth of her substantial fire powers. Firestorm/Killer Frost AU


**AN: So, I did an AU thing on Tumblr where I had to create story synopsis for different AU. One of them was a Klaroline superheroes AU, where I decided to write Caroline as Firestorm from DC, and Klaus as Killer Frost. Clearly, I ended up writing it. This will be 3 to a max of 5 chapters. I can handle writing that much.**

 **One**

" _Do you ever think this is a dream sometimes?"_

 _Klaus ran his fingers down Caroline's naked shoulder. They were in their bed, her back pressed firmly to his front, and he wasn't sure he had ever felt so…_ content _. He hummed thoughtfully and leaned down to kiss the skin his fingers had been caressing._

 _"No. I'm happy this is firmly rooted in reality."_

 _Caroline turned over in his arms, reached up to run a hand through his hair, and he swooped down to press feathering kisses over her eyelids, her nose, until, finally, he kissed her laughing lips._

 _"If this is a dream, don't let me wake up," she said when they broke apart._

 _"It's not a dream, Love," Klaus replied, entwining their fingers so they could both look at the diamond that glittered on her finger, a symbol of the promises they would be making each other in just one short week. "But I swear I'll keep you here with me."_

Fingers groped for air, seeking out her hand when her fingers seemed to vanish, and Klaus opened his eyes, to find his fingers reaching for an empty pillow and empty blankets.

Just as they had for six months.

There was no blonde beauty lying next to him, rolling her eyes when he exasperated her, or giggling when he kissed that sensitive spot below her ear. There was just emptiness.

Emptiness in his bed, emptiness inside of him.

 _And cold_. He was always so. Damn. Cold. He clenched his fingers, their surface glittering in the morning light that streamed through the window. Sometime in the night, his skin had changed from pale human flesh to the glittering permafrost that had haunted him since… just ever since.

He pulled himself to his feet and walked to the bathroom, opening the door and looking down at the young man tied up there. He looked up with fear when Klaus entered, and began to struggle against his bonds. Klaus could see reddening on his wrists, from where he must have tried to escape the night before, and shook his head slightly. At first, they had managed to occasionally get free. But he had gotten very good at knots.

"I'm sorry for this," he said to the young man, kneeling down in front of him. "But you see… I'm just so very _cold_."

He grasped the young man's face in his hands and reached out with the powers that welled in him, until he could feel the warmth sink into his frozen skin. The man screamed against the duct tape over his lips, agony ringing out in the small bathroom, but no one outside the apartment would hear.

Klaus watched as slowly, oh so slowly, the ice from his skin began to engulf the young man. Finally, Klaus clutched a frozen statue with skin that was once again normal. He looked at the statue for a moment, before pulling his hands away. As he did so, the ice shattered, scattering across the floor of the bathroom. Caroline would have hated it. She had always hated messes – _stress cleaning_ was a common practice for his love.

Klaus straightened and looked at himself in the mirror. The same face Caroline had fallen in love with, but not the same man. He looked away, thinking that she would hate what he had become.

By the time he left the apartment for work, the pieces of ice in his bathroom were melting into pool, and Klaus had once again convinced himself that what Caroline thought of him wouldn't matter.

The dead had no opinions.

TKS

"Niklaus."

Klaus sighed when he entered his office at the art gallery. His brother was sitting in his chair again. Elijah was forever worried about him, and how anti-social he had become since the night of Caroline's…

"What do you want, brother?" Klaus asked, hanging up his coat and turning to the desk. He kept a careful distance, the healthy color in his brother's cheeks acting like a beacon, and Klaus flexed his hand, a chill stealing through his fingertips.

He wished he could tell Elijah to stay away, but how was he to explain it?

 _Sorry, brother, but I isolate myself so I don't suck the life out of you and leave nothing but ice in your place._

The town had become overrun with the so-called meta-humans, and Elijah had not been quiet in his opinions on the people that had been affected by STAR Labs' particle accelerator.

"I came to ask for your assistance with the suit against STAR Labs. What happened to Caroline-"

"No," Klaus cut him off stonily, daring to venture close enough to the desk to pick up the inventory paperwork he needed to check against the gallery's newest deliveries.

"Niklaus, that… _place_ killed your fiancée, do you not wish for justice?"

Klaus just glared at him silently, because of course he wanted justice. His fiancée, the love of his _life_ was dead, leaving behind a man that lived off of stolen lives. But Caroline had loved STAR Labs. Had loved being able to use her doctorate in advanced phsyics to make _actual real life difference!_ If Klaus was to survive as a monster that Caroline would hate, then he would do so without destroying the place she had been so very dedicated to.

"Caroline is dead," he said, his voice breaking on the word. "Will this lawsuit of yours bring her back?"

"It may bring you some closure."

Klaus' laugh lacked any genuine mirth. He turned away from Elijah and looked down at his hand, and watched as, for a brief second, permafrost began to develop over the surface of his skin. He closed his eyes, concentrated on pushing back the cold, and felt a bone deep shiver run through him as the frost was once more replaced by human skin.

"There will be no closure for me, Elijah. Leave it be" – and then he hesitated, because he knew his brother would demand _why_ , and Klaus kept refusing to answer… but perhaps half the truth would do – "Caroline… she loved that place."

"And it killed her," Elijah replied, and Klaus recognized that stubborn timbre to his voice, the one that said Klaus wouldn't be wining this argument. Once he would have continued to argue anyway, determined that his brother not win… but that was before the very real threat he would freeze his brother to death with his anger had developed. "Just like it's killing this town… another disappearance, and I'd be willing to bet that it's one of those meta humans again."

Klaus turned back with a frown and a question on the tip of his tongue, but he froze when Elijah turned the monitor of the computer toward him, and hit play on a news story of a sobbing woman saying her boy had gone missing, and in the top right corner there was a picture of the boy Klaus had killed just that morning.

"This is the third one this week, and the other two haven't been found yet."

The third one this week? That couldn't be right… Klaus didn't even realize he'd stepped up right next to Elijah, until he actually felt his brother's warmth press against his skin, making him recoil.

"Dear Lord, Niklaus," Elijah said, staring at him. "You feel like ice."

"It's cold outside," Klaus replied stonily, turning away and storming away, desperate to get as far from his brother's tempting warmth as possible.

"It's July," he heard Elijah say somewhat incredulously, but Klaus didn't stop to reply.

His mind was too busy whirling around what Elijah had just said to him.

 _The third one this week_ … when the change had first happened, he had survived on just one life every two weeks. When had it grown to be so many?

He looked down and saw the frost glistening on his skin once more.

This time, when he concentrated, it didn't go away.

TKS

 _"And this, over here, is the particle accelerator. It's still a work in progress, but when it's complete… God, the things we'll be able to_ do _, Klaus!"_

 _Klaus watched as Caroline whirled around the lab, excitedly yammering away about the work she was doing, and thought that she had come a long way from the girl he'd known in her freshman year of university, when she had been a theatre major. She hadn't been nearly as excited about singing show tunes on a stage, as she was here in her labcoat, a pen stuck in her long blonde ponytail._

 _She was still entrancing, though._

 _He had planned to do this when they went for dinner… a surprise, for which he had reserved a table at her favorite Italian restaurant. But watching her, the way she lit up talking about her work – the way she simply lit up his world – made him realize there was only one place he should do that._

 _"And over here…" her words trailed off when she whirled around once more, to see him in front of her on one knee, perfect princess cut diamond held out for her to see._

 _For all that she had discovered she was a closet nerd in her second year of college, Caroline still had very exacting taste, and Klaus had known what her dream ring was almost as long as they had been dating._

 _"Klaus?" she asked with a whisper, her hands coming up to cover her mouth._

 _"Marry me, Caroline?" he asked, and found himself on his back, the floor not at all comfortable, but not caring. Because she was in his arms, peppering his face with kisses._

 _"Yes!" she said. "Yes! Of course it's yes!"_

 _Klaus laughed and sat up, and there on the floor of STAR Labs, he put the ring on her finger. They both sat there, hand entwined, admiring the ring._

 _The moment was absolutely perfect._

 _"I know you've always wanted a winter wonderland wedding," he told her, kissing her neck, and twirling her hair around a finger. "You've always loved the cold."_

When Klaus woke, his skin once more glittered like ice. He stared down at his hands for a moment, before he shoved his blankets away and rushed into the washroom. He stepped in a puddle – remnants from the boy of the previous day, but ignored it.

He looked into the mirror, and his reflection stared back at him with icy skin. He touched his hair, only to find that the curls Caroline had so loved to run her fingers through were instead short, hardened spikes. He stood there, staring, and then reeled back, his fist slamming into the mirror's reflective surface.

The glass shattered, pieces catching in his… _skin_. But it didn't hurt. It didn't do anything. He plucked the slivers out, and it were as though they had never been there. No pain, no blood… nothing to prove he was alive. Just _cold_.

Klaus let out an agonized shout and punched the mirror again, only there was no glass left, and instead his fist left a dent in the metal behind it. And still, Klaus felt nothing… nothing but cold.

He would need to feed again.

He wondered if it would even work, taking the warmth from a human. This felt _different_. This felt… _endless_. As though there were no way to fill the hole in his gut that felt so frozen.

He looked at his hands again, remembered how easily is previous victims had shattered…

When Klaus hit the ground from his sixteenth story window, he didn't shatter. He lay there instead, skin glittering in the morning sun, cement cracked around him, and heard someone come rushing toward him.

"Oh my God, are you oka-"

The Good Samaritan didn't even have time to scream before instinct and a desire for warmth gripped Klaus and propelled him from the ground. His hands locked around the woman's face, and he closed his eyes as he felt her warmth seep into his body, until there was nothing left. Until he released her and she shattered to a thousand pieces, just like every one of his victims before.

But this was the first time he'd had an audience. There weren't many – only a half dozen or so, that had come when they'd seen him fall from the window. But all Klaus could see was their warmth.

When he grabbed a second victim, the others scattered, screaming for help. It was a girl, probably only in her early twenties, and Klaus watched the light fade from her blue eyes, watched the ice engulf her blonde hair.

 _"I love you," Caroline laughed up at him, her hazel eyes glittering in the sun, her hair seeming to soak up the rays of light and reflect them back tenfold. For all that she loved the winter, there had never been a sight as beautiful as Caroline in the summer. "I really, really love you."_

Klaus' fingers stroked through the girl's blonde hair as it became ice, and he fell to his knees, her body in his arms. She shattered before he hit the ground, pieces mingling with the other woman's, and Klaus could only stare down at his hands, still glittering with ice, and loathe the monster he had become.

TKS

She had been wandering for what seemed like… _years_. She knew it hadn't been. Somewhere in the muddle her mind had become, she knew it hadn't been years. Only that it felt like it.

But there were so many voices. Well, two voices… but it was enough to make her clutch at her head, and then recoil when her skin sparked with fire, yet it didn't burn.

Sometimes, she could think clearly. When she was Bonnie, she could think clearly. It was only when the fire took over… then she wasn't Bonnie anymore. Then she didn't know who she was.

She was entirely different. No one would mistake her for Bonnie when the fire took over.

She called herself Firestorm then, and she prayed desperately that she didn't kill anyone when she was Firestorm.

She huddled in an alley, not because she needed warmth – Firestorm or Bonnie, she was always warm these days – but instead because she wanted to keep her distance from others, to protect herself from anyone getting too close. To protect _them_.

She knew better than to crawl out when she heard the screams, but both parts of her – Firestorm and Bonnie – had always been curious. So she wandered out. She saw the man fall, and blinked because she swore she saw blue skin that glinted like ice.

Then the other screams came, and this time they were filled with terror.

Bonnie hesitated, wanting to go back to the alley, but Firestorm… flames ignited around her, and she ignored the people that fled from her now, screams echoing, as she made her way into the other alley.

It was a man, and as she had thought… he had glinting blue skin. He was shaking, as though he were cold… or maybe as though he were crying, and when Firestorm stepped on ice that cracked beneath her boot – ice that surrounded him in scattered chunks – his head whipped around and ice covered the ground, swirling out from where his hand touched the pavement.

When he saw her, he froze, and Firestorm stared at him… there was something familiar… something in his eyes…

"Caroline," he croaked, and stumbled to his feet, his steps sluggish and dragging. Firestorm stood frozen, because she didn't know that name – _Caroline_ – yet something about it echoed in her mind, as though it were familiar.

Something about _him_ echoed in her mind.

 _"If you could be anything in the world, what would you be?"_

 _"Your husband… which I will be, in just one short month."_

 _"Klaus, I'm trying to be serious."_

Firestorm blinked, and then the man's arms were wrapped around her, and there were no more phantom conversations.

There was just _agony_.

She screamed, as his skin hit hers and seemed to… _suck_ at her. At the heat that made up her very core. She pulled back, only to find that his arms were like a vise, and his eyes were closed, the look on his face one of pure pleasure. She watched as his skin seemed to become pink and human, while hers began to turn blue, to grow heavy and pained, and she saw him – curly blonde hair, and when he opened his eyes they were blue, his smile dimpled – and his eyes widened when he saw what he was doing. When Firestorm gathered her energy into her center, and expelled it, it was far weaker than it had ever been, but it still sent him sliding back across the ground.

The blue slowly faded from her skin, until it only remained in her fingertips, as though she had developed frost bite. The man, still pink and human and oh-so healthy stared at her and got to his feet, making to move toward her again.

"Stay away," she snarled, calling flame around her, to keep him at a distance.

"Caroline-" he began, and Firestorm growled angrily, propelling herself into the air. She couldn't get the height or speed she usually did, but she still hovered out of his reach.

"I don't know who that is," she told him. "I don't _want_ to know who that is."

This… this _ice creature_ had hurt her, and Firestorm pitied the Caroline he thought she was, to be coveted by a monster.

 _"Maybe we should practice our vows."_

 _"I'm not telling you my vows."_

 _"Oh, c'mon Klaus. We should really be sure they align."_

 _"Not doing it."_

Firestorm shook her head. She had never had these conversations – conversations taking place with this man. She recognized that voice.

"You are Caroline Forbes," the man told her ( _Klaus_ , her mind supplied, but Firestorm ignored it). "You are my fiancée."

"I am your _nothing,_ " Caroline snarled back, and then her gaze was drawn to the ice, already melting into puddles, and the way her skin had begun to change…

 _She had stepped on his victims._

She wanted to be sick, but instead she just got _angry_. She looked at the man again, and gathered the heat with in, then swooped at him.

He went flying once more.

"Caroline-"

"I'm going to have to kill you," she told him, landing on the cement and stalking toward him. Something in her revolted at the very thought of harming him, making Firestorm _rage_. Because this man had killed others, so how could she possibly want him to live.

"Remember me, Caroline," the man pleaded, and he moved forward to grasp Firestorm's face, and pressed his lips to hers. It was so very, very familiar, this caress of his. It was like instinct, for Firestorm to reach up and rest her hands over his, to slant her lips at the perfect angle. It was like she had done this a hundred times. It was like everything that had happened didn't matter, because she was _made_ for this.

And then it happened again. The tug on her heat, the cold from his skin, and she shoved him once more. He looked at her, and he looked like he might be sick.

"I'm so sorry," he said, and the words made her pause when she would have hit him with flame again. As though she knew these were words that didn't come easy to him. Words rarely ever spoken in his voice.

Firestorm propelled herself up once more, and ignoring his calls behind her, she fled back to her alley. She stumbled in, falling to her knees in the blankets, and then Bonnie reached out and wrapped them around her and shoved herself back until she was in the shadows, Firestorm a simmering presence in the back of her mind.

When the man came rushing by, shouting out that name – _Caroline? Caroline?_ \- Bonnie shivered and cowered further, and whispered a thankful prayer when he moved on without noticing her.

And somewhere, deep within the mind of Bonnie Bennet and Firestorm… Caroline Forbes grieved for the man she loved.

 **AN: And there is the first part. Yes, Bonnie is the other Firestorm identity (for anyone that doesn't know – Firestorm is a fusion of a high school student and a genius physicist; in this case, Firestorm doesn't remember her life as Caroline). I took a lot of creative license with their powers and backstory, because I don't read the comics. Backstory is loosely borrowed from Caitlyn and Ronnie from** _ **The Flash**_ **(basically I took the engaged part).**

 **Let me know what you think.**


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